Predicting the Long-Term Evolution of a Barrier Spit in a Changing Climate: A Case Study in Napatree Point, Rhode Island

Shoreline recession poses a substantial threat to coastal communities. This study evaluates the long-term viability of the undeveloped Napatree barrier spit in Rhode Island, which provides critical habitat for both flora and fauna, including endangered species, and protects the small town of Westerly from the direct impact of tropical storms and Nor’easters. While the Napatree shoreline has been morphologically stable in recent decades (1970–present), historical periods of higher storm frequency and intensity had resulted in significant changes, including spit splitting and significant transgression. We use the one-line numerical model ShorelineS to assess long-term changes in the position of the Napatree shoreline. The model is calibrated and validated using 30 years of historical observations and then applied to estimate expected shoreline positions in the near future (approximately 2050), considering projected sea level rise (SLR) and potential changes in wave climate and storm frequency. Despite the past and current stability of the dune system, under projected SLR and changes in wave climate, the barrier is expected to recede, possibly reaching a tipping point in the forthcoming decades when its viability would be threatened. This would increase flood risks to the inland community, including critical infrastructures and residential areas. Results suggest that storm intensification rather than SLR is the primary factor of accelerating shoreline recession—by a factor of 4—compared with SLR-only scenarios.